The objective of this study was to determine normal impedance on the surface as well as sound absorption coefficients for several wood species from Europe and from the tropical zone. The mathematical models of Miki, Attenborough, and Allard – dealing with acoustic properties of porous materials – have also been compared. The air flow resistivity exhibits a distinct link between fiber dimensions and wood porosity. The highest sound absorption coefficient was found for oak, ash, sapeli, and pine woods at 2 kHz frequency. The Attenborough model provides results closest to laboratory measurements, although it still requires significant improvements. The Miki and Allard models have some drawbacks and should be applied with reservation for the determination of wood acoustic properties.
The problem of estimation of the long-term environmental noise hazard indicators and their uncertainty is presented in the present paper. The type A standard uncertainty is defined by the standard deviation of the mean. The rules given in the ISO/IEC Guide 98 are used in the calculations. It is usually determined by means of the classic variance estimators, under the following assumptions: the normality of measurements results, adequate sample size, lack of correlation between elements of the sample and observation equivalence. However, such assumptions in relation to the acoustic measurements are rather questionable. This is the reason why the authors indicated the necessity of implementation of non-classical statistical solutions. An estimation idea of seeking density function of long-term noise indicators distribution by the kernel density estimation, bootstrap method and Bayesian inference have been formulated. These methods do not generate limitations for form and properties of analyzed statistics. The theoretical basis of the proposed methods is presented in this paper as well as an example of calculation process of expected value and variance of long-term noise indicators LDEN and LN . The illustration of indicated solutions and their usefulness analysis were constant due to monitoring results of traffic noise recorded in Cracow, Poland.
The acoustic climate assessment needed for the selection of solutions (technical, legal and organisational), which will help to minimise the acoustic hazards in the analysed areas, is realised on the basis of acoustic maps. The reference computational algorithms, assigned to them, require very thorough preparation of input data for the considered noise source model representing -in the best possible way -the acoustic climate. These input data are burdened with certain uncertainties in this class of computational tasks. The uncertainties are related to the problem of selecting proper argument values (from the interval of their possible variability) for the modelled processes. This situation has a direct influence on the uncertainty of acoustic maps.The idea of applying the interval arithmetic for the assessment of acoustic models uncertainty is formulated in this paper. The computational formalism assigned to the interval arithmetic was discussed. The rules of interval estimations for the model solutions determining the sound level distribution around the analysed noise source -caused by possible errors in the input data -were presented. The application of this formalism was illustrated in uncertainty assessments of modelling acoustic influences of the railway noise linear source on the environment.
The paper formulates some objections to the methods of evaluation of uncertainty in noise measurement which are presented in two standards : ISO 9612 (2009) and DIN 45641 (1990). In particular, it focuses on approximation of an equivalent sound level by a function which depends on the arithmetic average of sound levels. Depending on the nature of a random sample the exact value of the equivalent sound level may be significantly different from an approximate one, which might lead to erroneous estimation of the uncertainty of noise indicators. The article presents an analysis of this problem and the adequacy of the solution depending on the type of a random sample.
Assessment of several noise indicators are determined by the logarithmic mean10 0.1L i , from the sum of independent random results L1, L2, . . . , Ln of the sound level, being under testing. The estimation of uncertainty of such averaging requires knowledge of probability distribution of the function form of their calculations. The developed solution, leading to the recurrent determination of the probability distribution function for the estimation of the mean value of noise levels and its variance, is shown in this paper.
This study is dedicated to the problem of estimating uncertainties of long-term noise indicators, when differences in the sound level emission at various time periods of the calendar year are taken into consideration. This task is defined by referring their influence values -in the determined time intervals -to the year period. Due to the limited possibilities of a total monitoring of parameters necessary for the precise estimation of the long-term sound levels, this estimation process is often limited (in accordance with the EU environmental recommendations) to two condition classes. They are defined by two sound levels occurring with probabilities (frequencies) p and 1 − p, in the analyzed reference period. In this paper we present a method of calculating uncertainties of this procedure assuming that frequency of determined events are known. The probability distribution for the estimated value was assessed. The developed model formalism of the estimation of uncertainties of long-term sound levels together with algorithms assigned to it, was analyzed. The proposed solution was illustrated by examples of uncertainty calculations of the averaged sound levels in acoustic assessments of environmental hazards.
Objectives: The aim of the study was the assessment of lung ultrasound (LUS) as a screening of pulmonary interstitial involvement secondary to systemic connective tissue diseases. Methods: A prospective study was conducted on the study group comprising 180 patients diagnosed with different systemic connective tissue diseases. Each patient underwent lung ultrasound (LUS), high-resolution chest computed tomography (HRCT), and echocardiography (ECHO). Each imaging examination was blinded and performed by an independent operator. LUS was conducted with convex and linear transducers. Results: The sensitivity and specificity of LUS as compared to HRCT in detecting pulmonary interstitial involvement in the study group were 99.3% and 96.4%, respectively; positive predictive value (PPV) 0.7, negative predictive value (NPV) 3.6. Abnormalities indicating interstitial lung disease (ILD) with fibrosis were most frequently localized bilaterally in the lower fields of the lungs, assessed in the dorsal view. Conclusions: LUS is an efficient imaging modality that can detect pulmonary interstitial involvement in patients with systemic connective tissue disease with a high sensitivity and specificity. Further prospective studies conducted on a larger population are deemed necessary.
Uncertainty assessment in modelling of acoustic phenomena with uncertain parameters using interval arithmetic on the example of the reverberation time estimation, are presented in the paper. The application of the classical interval analysis formalism as well as its expansions are shown. Statistical methods of estimation of the reverberation time are based on parameters, which are related, among others, to the geometry of the analysed room, characteristics of sound absorption, and interior transmission. Values of these parameters are usually dicult to determine, which has a signicant inuence on the modelling result. The interval analysis allows to determine the variability interval of the parameter being estimated. The authors determined the inuence of the input parameters uncertainty on the estimated reverberation time, calculated according to the Sabine, EyringNorris and MillingtonSette formulae. The uncertainty analysis was performed for the literature data, related to the reverberation time calculations of the room of a certied acoustics. PACS: 43.28.Lv, 43.55.Br
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